The risks of drink-driving are clear for any sensible motorist and no-one with a bit of intelligence would use the car when going out partying.

However, a less obvious danger is that of the "morning after"- drink-drive accidents in which people drive not knowing they may still be over the legal limit. A threat we should be specially aware of now that we are into the Christmas party season.

New research shows figures of a 60% increase in the proportion of morning-after crashes in the last 10 years.

According to the personal breathalyser retailer AlcoSense, 18.2% of all accidents caused by drink-driving in 2010 occurred between 5am and 1pm. In 2000 the figure was 11.4% and in 1990, 6.9% for the same time interval.

So when things seemed to get better - the proportion of drink-drive accidents occurring in the afternoon and evening have fallen by just over 10% over the past two decades - we discover that the problem has only been shifted forward to the next day.

The breathalyser company explains this fact referring to the changes in licensing laws. Their research shows a sharp increase in the morning after accident rate since 2005, when pubs and bars started to be allowed to stay open later.

AlcoSense Managing Director Hunter Abbott said: "People still believe however that a few hours' sleep will get rid of all of the alcohol in their system but it is surprisingly easy to still be over the limit the 'morning after'.

For example if you drank 4 pints of medium strong beer or 4 large glasses of wine between 9pm and midnight, it could take as long as 14.8 hours for the alcohol to leave your system. Therefore you could easily still be over the limit at 11am the following day," he added.

Road safety charity Brake spokesperson, Richard Coteau, said: "We were shocked by the increase in morning after drink-driving - which is now a serious problem. Nearly one in six of all deaths on the road involve drivers who are over the legal alcohol limit. Any amount of alcohol in your system affects your ability to drive, even if it's from the night before. We want to encourage people to test now, drive later and avoid driving the morning after a night out drinking alcohol."